Electrostatic and van der Waals (vdW) interactions are two major components of intermolecular weak interactions. Electrostatic potential has been a very popular function in revealing electrostatic interaction between the system under study and other species, while the role of vdW potential is less recognized and has long been ignored. In this paper, we explicitly present definition of vdW potential, describe its practical implementation, and demonstrate its important value by visual analysis and comparing it with spatial distribution function obtained via molecular dynamics simulation. We hope this work can arouse researchers' attention to van der Waals potential and promote its application in practical studies of weak interaction. Calculation, visualization and quantitative analysis of the vdW potential have been supported by our freely available code Multiwfn (http://sobereva.com/multiwfn).